Chiral covalent organic frameworks: design, synthesis and property

Owing to the unique structural features and facile tunability of the subcomponents and channels, chiral COFs show great potential in heterogeneous catalysis, enantioselective separation, and recognition.

Crystalline C-C and C═C Bond-Linked Chiral Covalent Organic Frameworks

While crystalline covalent organic frameworks (COFs) linked by C-C bonds are highly desired in synthetic chemistry, it remains a formidable challenge to synthesize. Efforts to generate C-C single bonds in COFs via de novo synthesis usually afford amorphous structures rather than crystalline phases. We demonstrate here that C-C single bond-based COFs can be prepared by direct reduction of C═C bond-linked frameworks via crystal-to-crystal transformation. By Knoevenagel polycondensation of chiral tetrabenzaldehyde of dibinaphthyl-22-crown-6 with 1,4-phenylenediacetonitrile or 4,4'-biphenyldiacetonitrile, two olefin-linked chiral COFs with 2D layered tetragonal structure are prepared. Reduction of olefin linkages of the as-prepared CCOFs produces two C-C single bond linked frameworks, which retains high crystallinity and porosity as well as high chemical stability in both strong acids and bases. The quantitative reduction is confirmed by Fourier transform infrared and cross-polarization magic angle spinning ¹³C NMR spectroscopy. Compared to the pristine structures, the reduced CCOFs display blue-shifted emission with enhanced quantum yields and fluorescence lifetimes, while the parent CCOFs exhibit higher enantioselectivity than the reduced analogs when be used as fluorescent sensors to detect chiral amino alcohols via supramolecular interactions with the built-in crown ether moieties. This work provides an attractive strategy for making chemically stable functionalized COFs with new linkages that are otherwise hard to produce.

How Reproducible are Surface Areas Calculated from the BET Equation?

Porosity and surface area analysis play a prominent role in modern materials science. At the heart of this sits the Brunauer-Emmett-Teller (BET) theory, which has been a remarkably successful contribution to the field of materials science. The BET method was developed in the 1930s for open surfaces but is now the most widely used metric for the estimation of surface areas of micro- and mesoporous materials. Despite its widespread use, the calculation of BET surface areas causes a spread in reported areas, resulting in reproducibility problems in both academia and industry. To prove this, for this analysis, 18 already-measured raw adsorption isotherms were provided to sixty-one labs, who were asked to calculate the corresponding BET areas. This round-robin exercise resulted in a wide range of values. Here, the reproducibility of BET area determination from identical isotherms is demonstrated to be a largely ignored issue, raising critical concerns over the reliability of reported BET areas. To solve this major issue, a new computational approach to accurately and systematically determine the BET area of nanoporous materials is developed. The software, called "BET surface identification" (BETSI), expands on the well-known Rouquerol criteria and makes an unambiguous BET area assignment possible.

Use of MR spectroscopy and functional imaging in the treatment planning of gliomas

Routine anatomical imaging with CT and MRI does not reliably indicate the true extent or the most malignant areas of gliomas and cannot identify the functionally critical parts of the brain. The aim of the study was to see if the use of MR spectroscopic imaging (MRSI) along with functional MRI (fMRI) can better define both the target and the critical structures to be avoided to improve radiation delivery in gliomas. 12 patients with gliomas underwent multivoxel MRS and functional imaging using GE processing software. The choline to creatine ratio (Cho:Cr), which represents the degree of abnormality for each individual voxel on MRSI, was derived, converted into a grayscale grading system, fused to the MRI images and then transferred to the planning CT images. An intensity-modulated radiation therapy (IMRT) plan was developed using the dose constraints based on both the anatomical and the functionally critical regions. Cho:Cr consistently identified the gross tumour volume (GTV) within the microscopic disease (clinical target volume, CTV) and allowed dose painting using IMRT. No correlation between MRSI based Cho:Cr > or =2 and MR defined CTV nor their location was noted. However, MRSI defined Cho:Cr > or =3 was smaller by 40% compared with post-contrast T1 weighted MRI defined GTV volumes. fMRI helped in optimizing the orientation of the beams. In conclusion, both MRSI and fMRI provide additional information to conventional imaging that may guide dose painting in treatment planning of gliomas. A Phase I IMRT dose intensification trial in gliomas using this information is planned.

Coherent control of plasma dynamics

Coherent control of a system involves steering an interaction to a final coherent state by controlling the phase of an applied field. Plasmas support coherent wave structures that can be generated by intense laser fields. Here, we demonstrate the coherent control of plasma dynamics in a laser wakefield electron acceleration experiment. A genetic algorithm is implemented using a deformable mirror with the electron beam signal as feedback, which allows a heuristic search for the optimal wavefront under laser-plasma conditions that is not known a priori. We are able to improve both the electron beam charge and angular distribution by an order of magnitude. These improvements do not simply correlate with having the 'best' focal spot, as the highest quality vacuum focal spot produces a greatly inferior electron beam, but instead correspond to the particular laser phase front that steers the plasma wave to a final state with optimal accelerating fields.

Confinement-Driven Enantioselectivity in 3D Porous Chiral Covalent Organic Frameworks

3D covalent organic frameworks (COFs) with well-defined porous channels are shown to be capable of inducing chiral molecular catalysts from non-enantioselective to highly enantioselective in catalyzing organic transformations. By condensations of a tetrahedral tetraamine and two linear dialdehydes derived from enantiopure 1,1'-binaphthol (BINOL), two chiral 3D COFs with a 9-fold or 11-fold interpenetrated diamondoid framework are prepared. Enhanced Brønsted acidity was observed for the chiral BINOL units that are uniformly distributed within the tubular channels compared to the non-immobilized acids. This facilitates the Brønsted acid catalysis of cyclocondensation of aldehydes and anthranilamides to produce 2,3-dihydroquinazolinones. DFT calculations show the COF catalyst provides preferential secondary interactions between the substrate and framework to induce enantioselectivities that are not achievable in homogeneous systems.

MiR-133b ameliorates axon degeneration induced by MPP(+) via targeting RhoA

Increasing evidence suggests that microRNAs (miRs) play a significant role in the pathogenesis of Parkinson's disease (PD). MiR-133b, which is significantly decreased in the PD midbrain, has recently been shown to promote neurite outgrowth and enhance neural functional recovery. However, the role of miR-133b in PD has not been clearly established. Here, using a well-established PD model culture based on the neurotoxin 1-methyl-4-phenyl-pyridinium (MPP(+)), we demonstrated that miR-133b could promote axon outgrowth in dopaminergic neurons (DNs) and ameliorated MPP(+)-induced axon degeneration. Additional experiments suggested that the mechanisms of this miR-133b-mediated effect might rely on RhoA inhibition. We demonstrated that RhoA, an inhibitor of axonal growth, was increased in DNs under MPP(+) treatment, and this increase could be attenuated by miR-133b overexpression. Moreover, we demonstrated that the induced expression of miR-133b could inhibit α-synuclein, which is critically involved in the pathological process of PD. Furthermore, we found that overexpression of miR-133b abrogated the MPP(+)-induced decrease in the Bcl-2/Bax ratio and upregulated phosphorylated Akt (p-Akt), which is a pro-survival kinase. Together these findings reveal novel roles for miR-133b in the pathogenesis of PD and provide new therapeutic avenues for the treatment of the disease.

Amino-Nogo-A antagonizes reactive oxygen species generation and protects immature primary cortical neurons from oxidative toxicity

Nogo-A is originally identified as an inhibitor of axon regeneration from the CNS myelin. Nogo-A is mainly expressed by oligodendrocytes, and also by some neuronal subpopulations, particularly in the developing nervous system. Although extensive studies have uncovered regulatory roles of Nogo-A in neurite outgrowth inhibition, precursor migration, neuronal homeostasis, plasticity and neurodegeneration, its cell-autonomous functions in neurons are largely uncharacterized. Here, we show that HIV-1 trans-activating-mediated amino-Nogo-A protein transduction into cultured primary cortical neurons achieves an almost complete neuroprotection against oxidative stress induced by exogenous hydrogen peroxide (H(2)O(2)). Endogenously expressed neuronal Nogo-A is significantly downregulated upon H(2)O(2) treatment. Furthermore, knockdown of Nogo-A results in more susceptibility to acute oxidative insults and markedly increases neuronal death. Interacting with peroxiredoxin 2 (Prdx2), amino-Nogo-A reduces reactive oxygen species (ROS) generation and extracellular signal-regulated kinase phosphorylation to exert neuroprotective effects. Structure-function mapping experiments reveal that, out of NiG-Δ20, a novel region comprising residues 290-562 of amino-Nogo-A is indispensable for preventing oxidative neuronal death. Moreover, mutagenesis analysis confirms that cysteine residues 424, 464 and 559 are involved in the inhibition of ROS generation and neuroprotective role of amino-Nogo-A. Our data suggest that neuronal Nogo-A might play a cell-autonomous role in improving neuronal survival against oxidative insult through interacting with Prdx2 and scavenging of ROS.

Bacterial proteins carrying twin-R signal peptides are specifically targeted by the delta pH-dependent transport machinery of the thylakoid membrane system

Glucose-fructose oxidoreductase (GFOR), a periplasmic protein of Zymomonas mobilis, is synthesized as a precursor polypeptide with a twin-R signal peptide for Sec-independent protein export in bacteria. In higher plant chloroplasts, twin-R signal peptides are specific targeting signals for the Sec-independent delta pH pathway of the thylakoid membrane system. In agreement with the assumed common phylogenetic origin of the two protein transport mechanisms, GFOR can be efficiently translocated by the delta pH-dependent pathway when analyzed with isolated thylakoid membranes. Transport is sensitive to the ionophore nigericin and competes with specific substrates for the delta pH-dependent transport route. In contrast, neither sodium azide nor enzymatic destruction of the nucleoside triphosphates in the assays affects thylakoid transport of GFOR indicating that the Sec apparatus is not involved in this process. Mutagenesis of the twin-R motif in the GFOR signal peptide prevents membrane translocation of the protein emphasizing the importance of these residues for the transport process.

Vasopressin autoreceptors and nitric oxide-dependent glutamate release are required for somatodendritic vasopressin release from rat magnocellular neuroendocrine cells responding to osmotic stimuli

Magnocellular neuroendocrine cells of the supraoptic nucleus (SON) release vasopressin (VP) systemically and locally during osmotic challenge. Although both central VP and nitric oxide (NO) release appear to reduce osmotically stimulated systemic VP release, it is unknown whether they interact locally in the SON to enhance somatodendritic release of VP, a phenomenon believed to regulate systemic VP release. In this study, we examined the contribution of VP receptor subtypes and NO to local VP release from the rat SON elicited by systemic injection of 3.5 m saline. Treatment of SON punches with VP receptor antagonists decreased osmotically stimulated intranuclear VP release. Similarly, blockade of NO production, or addition of NO scavengers, reduced stimulated VP, glutamate, and aspartate release, suggesting that local NO production and activity are critical for osmotically induced intranuclear VP and excitatory amino acid release. An increase in endogenous NO release from SON punches in response to hyperosmolality was confirmed by enzymatic NO assay. Consistent with enhanced glutamate and VP release from stimulated rat SON punches, the ionotropic glutamate receptor blocker kynurenate decreased stimulated local VP release without affecting NO release. These data suggest that NO enhances local VP release in part by facilitating local release of glutamate/aspartate and that glutamate receptor activity is required for the stimulation of local VP release by osmotic challenge. Collectively, these results suggest that local VP receptors, NO, and glutamatergic signaling mediate the amplification of intranuclear VP release during hyperosmolality and may contribute to efficient, but not exhaustive, systemic release of VP during osmoregulatory challenge.

The role of platelet MyD88 in host response during gram-negative sepsis

BACKGROUND

Beside their role in hemostasis, platelets serve as sentinel cells in host defense during infection. In sepsis, platelets have been implicated in both beneficial (antibacterial) and detrimental responses (thrombosis and organ damage). Toll-like receptors and their common adaptor, myeloid differentiation factor 88 (MyD88), are essential for pathogen recognition and protective immunity. Platelets express functional Toll-like receptors and MyD88, which participate in platelet responsiveness to bacterial agonists.

OBJECTIVE

Considering the pivotal involvement of platelets and MyD88 in the host response to bacteria, we studied the role of platelet MyD88 in gram-negative sepsis using intravenous and airway infections with the common human sepsis pathogen Klebsiella pneumoniae.

METHODS

Platelet-specific Myd88(-/-) mice were generated by crossing mice with a conditional Myd88 flox allele with mice expressing Cre recombinase controlled by the platelet factor 4 promoter. In a reverse approach, full Myd88(-/-) mice were transfused with wild-type platelets.

RESULTS

In both settings, platelet MyD88 did not impact on bacterial growth or dissemination. In addition, platelet MyD88 did not influence hallmark sepsis responses such as thrombocytopenia, coagulation or endothelial activation, or distant organ injury. Platelet MyD88 played no role in lung pathology during pneumonia-derived sepsis.

CONCLUSION

Despite known literature, platelet MyD88-dependent TLR signaling does not contribute to the host response during gram-negative sepsis.

Relativistic generation of isolated attosecond pulses in a lambda 3 focal volume

Lasers that provide an energy encompassed in a focal volume of a few cubic wavelengths (lambda(3)) can create relativistic intensity with maximal gradients, using minimal energy. With particle-in-cell simulations we found, that single 200 attosecond pulses could be produced efficiently in a lambda(3) laser pulse reflection, via deflection and compression from the relativistic plasma mirror created by the pulse itself. An analytical model of coherent radiation from a charged layer confirms the pulse compression and is in good agreement with simulations. The novel technique is efficient (approximately 10%) and can produce single attosecond pulses from the millijoule to the joule level.

Interindividual reaction time variability is related to resting-state network topology: an electroencephalogram study

Both anatomical and functional brain network studies have drawn great attention recently. Previous studies have suggested the significant impacts of brain network topology on cognitive function. However, the relationship between non-task-related resting-state functional brain network topology and overall efficiency of sensorimotor processing has not been well identified. In the present study, we investigated the relationship between non-task-related resting-state functional brain network topology and reaction time (RT) in a Go/Nogo task using an electroencephalogram (EEG). After estimating the functional connectivity between each pair of electrodes, graph analysis was applied to characterize the network topology. Two fundamental measures, clustering coefficient (functional segregation) and characteristic path length (functional integration), as well as "small-world-ness" (the ratio between the clustering coefficient and characteristic path length) were calculated in five frequency bands. Then, the correlations between the network measures and RT were evaluated in each band separately. The present results showed that increased overall functional connectivity in alpha and gamma frequency bands was correlated with a longer RT. Furthermore, shorter RT was correlated with a shorter characteristic path length in the gamma band. This result suggested that human RTs were likely to be related to the efficiency of the brain integrating information across distributed brain regions. The results also showed that a longer RT was related to an increased gamma clustering coefficient and decreased small-world-ness. These results provided further evidence of the association between the resting-state functional brain network and cognitive function.

Non-isomerizable artificial pigments: implications for the primary light-induced events in bacteriorhodopsin

The primary events in the photosynthetic retinal protein bacteriorhodopsin (bR) are reviewed in light of photophysical and photochemical experiments with artificial bR in which the native retinal polyene is replaced by a variety of chromophores. Focus is on retinals in which the "critical" C13=C14 bond is locked with respect to isomerization by a rigid ring structure. Other systems include retinal oxime and non-isomerizable dyes noncovalently residing in the binding site. The early photophysical events are analyzed in view of recent pump-probe experiments with sub-picosecond time resolution comparing the behavior of bR pigments with those of model protonated Schiff bases in solution. An additional approach is based on the light-induced cleavage of the protonated Schiff base bond that links retinal to the protein by reacting with hydroxylamine. Also described are EPR experiments monitoring reduction and oxidation reactions of a spin label covalently attached to various protein sites. It is concluded that in bR the initial relaxation out of the Franck-Condon (FC) state does not involve substantial C13=C14 torsional motion and is considerably catalyzed by the protein matrix. Prior to the decay of the relaxed fluorescent state (FS or I state), the protein is activated via a mechanism that does not require double bond isomerization. Most plausibly, it is a result of charge delocalization in the excited state of the polyene (or other) chromophores. More generally, it is concluded that proteins and other macromolecules may undergo structural changes (that may affect their chemical reactivity) following optical excitation of an appropriately (covalently or non-covalently) bound chromophore. Possible relations between the light-induced changes due to charge delocalization, and those associated with C13=C14 isomerization (that are at the basis of the bR photocycle), are discussed. It is suggested that the two effects may couple at a certain stage of the photocycle, and it is the combination of the two that drives the cross-membrane proton pump mechanism.

FAM83H overexpression predicts worse prognosis and correlates with less CD8+ T cells infiltration and Ras-PI3K-Akt-mTOR signaling pathway in pancreatic cancer

BACKGROUND

Family with sequence similarity 83 members H (FAM83H) is one member of Family with sequence similarity 83 (FAM83) family, which possess oncogenic properties in several types of cancer. However, the potential function of FAM83H in pancreatic cancer (PC) still remain unknown.

AIM

This study aims to explore the role of FAM83H during pancreatic carcinogenesis and the regulation of immune infiltration in PC.

METHODS

In the current study, the clinical significance and potential biological of FAM83H were evaluated by bioinformatics analysis. Possible associations between FAM83H expression and tumor immunity were analyzed using ESTIMATE algorithm and single-sample gene set enrichment analysis (ssGSEA).

RESULTS

FAM83H expression was significantly upregulated in tumor tissues, and positively associated with higher histologic grade, tumor recurrence, and worse prognosis. FAM83H overexpression is notably associated with KRAS activation. And functional enrichment analysis demonstrated that FAM83H may be involved in positive regulation of cell proliferation and migration, Ras protein signal transduction, regulation of cell-matrix adhesion, epithelial to mesenchymal transition (EMT), TGF-β receptor signaling in EMT, and activated NOTCH transmits signal to the nucleus. ESTIMATE algorithm and ssGSEA demonstrated that FAM83H overexpression suppressed the infiltration and antitumor activity of tumor-infiltrating lymphocytes (TILs), especially for CD8⁺ T cells. Besides, FAM83H overexpression significantly correlated with low expression of TIL-related gene markers (e.g. CD8A, CD8B, CD2, CD3D, and CD3E).

CONCLUSION

The study suggests that FAM83H overexpression predicts poor prognosis and correlates with less CD8⁺ T cells infiltration and Ras-PI3K-Akt-mTOR signaling pathway in PC.

Rapid identification of Sporothrix schenckii in biopsy tissue by PCR

BACKGROUND

The dimorphic fungus Sporothrix schenckii is the etiological agent of sporotrichosis, an important cutaneous mycosis with a worldwide distribution. At present, it is challenging to rapidly discover and identify Sporothrix schenckii in biopsy tissues nowadays.

AIMS

To explore new methods for rapid diagnosis of sporotrichosis.

MATERIALS AND METHODS

We screened specific primers for Sporothrix schenckii using 50 clinical isolates from patients with sporotrichosis. DNA was extracted from the lesions of 30 cases of clinically suspected sporotrichosis using the Graham s method of CTAB and amplified by PCR using the screened specific primers.

RESULTS

The primer S2-R2 was applicable for the identification of S. schenckii from different geographic areas and clinical types with high specificity and sensitivity. Twenty-five out of the thirty cases (83.3%) amplified using the primer S2-R2 showed positive bands. Further positive bands were observed in 95.6% of cases tested positive by fungal culture.

CONCLUSIONS

Using the PCR technique and specific primers, we developed a new diagnostic method that can rapidly diagnose sporotrichosis with tissues obtained from clinical biopsies.

Positive feedback regulation between microRNA-132 and CREB in spinal cord contributes to bone cancer pain in mice

BACKGROUND

cAMP response element-binding protein (CREB)-dependent gene expression plays an important role in central sensitization. CREB-regulated transcription coactivator 1 (CRTC1) dramatically increase CREB-mediated transcriptional activity. microRNA-132 (miR-132), which is highly CREB-responsive, functions downstream from CREB/CRTC1 to mediate activity-dependent synaptic plasticity and in turn loops back to amplify CREB/CRTC1 signalling. This study aimed to investigate the positive feedback regulation between miR-132 and CREB in spinal cord in the maintenance of bone cancer pain.

METHODS

Osteosarcoma cells were implanted into the intramedullary space of the right femurs of C3H/HeNCrlVr mice to induce bone cancer pain. We further investigated effects of repeated intrathecal administration with Adenoviruses expressing CREB-siRNA or miR-132 antisense locked nucleic acid (LNA), respectively, on nociceptive behaviours and on the activity of CREB/CRTC1 signalling.

RESULTS

Intramedullary inoculation of osteosarcoma cells resulted in up-regulation of spinal p-CREB, CRTC1 and CREB-target genes (NR2B and miR-132). Repeated intrathecal administration with Adenoviruses expressing CREB-siRNA or miR-132 LNA-AS, respectively, attenuated bone cancer-evoked pain behaviours, reduced the activity of CREB/CRTC1 signalling and down-regulated CREB-target gene NR2B expression in spinal cord.

CONCLUSIONS

These findings suggest that activation of spinal CREB/CRTC1 signalling may play an important role in bone cancer pain. Interruption to the positive feedback regulation between CREB/CRTC1 and its target gene miR-132 can effectively relieved the bone cancer-induced mechanical allodynia and spontaneous pain. WHAT DOES THIS STUDY ADD?: The positive feedback regulation between CREB/CRTC1 and its target gene miR-132 in spinal cord plays an important role in bone cancer pain.

Bacillus licheniformis Zhengchangsheng® attenuates DSS-induced colitis and modulates the gut microbiota in mice

Human inflammatory bowel disease (IBD) and experimental colitis models in mice are associated with shifts in gut microbiota composition, and several probiotics are widely used to improve gastrointestinal health. Here, we investigated whether the probiotic Bacillus licheniformis Zhengchangsheng® (BL) ameliorates dextran sulphate sodium (DSS)-induced colitis through alteration of the gut microbiota. Experimental colitis was induced in BALB/C mice by dissolving 3% DSS in their drinking water for 7 days, which were gavaged with 0.2 ml phosphate-buffered saline or BL (3×107 cfu/ml) once a day. Administration of BL attenuated several effects of DSS-induced colitis, including weight loss, increased disease activity index, and disrupted intestinal barrier integrity. In addition, BL mitigated the reduction in faecal microbiota richness in DSS treated mice. Interestingly, BL was found to reduce the elevated circulating endotoxin level in mice with colitis by modulating the microbial composition of the microbiota, and this was highly associated with a proportional decrease in gut Bacteroidetes. Our results demonstrate that BL can attenuate DSS-induced colitis and provide valuable insight into microbiota interactions during IBD.